The present invention relates to devices, in particular substrate contacts and shielding devices, in a semiconductor component and methods of manufacturing these. Furthermore, the invention relates to a method of arranging substrate contacts.
In manufacturing silicon components being densely packed it is of great importance to avoid undesired coupling between different blocks of components located on the same silicon substrate. Such an undesired coupling or xe2x80x9ccross-talkxe2x80x9d between different blocks is most often more inconvenient in the manufacturing of analogue digital integrated circuits (IC) of a so called mixed-mode type. Cross-talk between different circuit blocks can either take place via capacitive coupling between the connection conductors or via substrate coupling. A number of different approaches for minimizing cross-talk, via the substrate, are described in literature, see for example K. Joardar; xe2x80x9cA simple approach to modeling cross-talk in integrated circuitsxe2x80x9d, IEEE J. Solid State Circuits. vol. 29, 1994, pp. 1212.
It is characteristic of all described techniques that different types of isolation methods in combination with substrate contacts for suppressing cross-talk are used. In addition to having good isolation between the respective blocks it is also required that the subtract contact is made as low-resistant as possible in order to achieve the best possible result.
The drawback with the methods described in the paper mentioned above, is that the contact resistance between the metal and substrate becomes comparatively high, since doped silicon, a P-plug, is used as connection. Said diffusion of a P-type must also be made having a depth of several xcexcm in order to secure contact between a high-doped substrate and metal. This requires a long drive-in diffusion time in combination with a high drive-in diffusion temperature which is not desirable in the manufacturing of modern components where a low temperature budget is aimed at. Last but not least, the P+-diffusion, i.e. the so called guard-ring, is space demanding, since lateral diffusion takes place simultaneously with the vertical diffusion.
It is an object of the present invention to provide a low-resistant substrate contact for semiconductor components which overcomes the drawbacks arising when forming substrate contacts according to prior art.
It is further an object of the present invention to provide a method of locating and arranging these substrate contacts around a component or a block of components in order to obtain a good shielding between different components or blocks of components.
These and other objects are obtained using a substrate contact made of metal, extending deep down into the underlying semiconductor material, all the way down into the substrate. Furthermore, by means of locating several such metallic substrate contacts at close intervals around components or blocks of components effective shielding towards undesired coupling or cross-talk is achieved.
Thus, a semiconductor component is obtained in a usual manner by means of using different substructures at and/or on a surface of a substrate. There is an electrical connection in the shape of a plug of a material with good electrical conductivity between the substrate and the surface at and/or next to the semiconductor component. The material can be of another type than the substrate, which typically is semiconductive and can have different types of doping. The plug is preferably a metal plug and in any case extends from an inner part of the substrate to an area close to the surface next to or at the semiconductor component. Furthermore, the plug should extend deeper down into the substrate than into the PN-junctions introduced and/or existing in the substrate. Several such plugs are preferably arranged around the surface of the semiconductor component and can then serve as electrical shielding of the semiconductor component. Furthermore, the upper ends of the plugs are preferably electrically connected as by means of layers or paths of an electrically conducting material, which as above can be a material with good electrical conductivity, in particular a metal material.
In the manufacturing of the plugs, suitably shaped holes are first made and which then are filled with the electrically conducting material.
The filling is preferably provided at the same time as other contact holes for electrical contact with different electrodes in the semiconductor are filled. Holes can then be made having a diameter or largest across corner dimension, which essentially corresponds to the corresponding measures for the contact holes. In any event the diameters of the holes should be chosen so that they are completely filled in the process step for filling the contact holes.
Plugs of the above mentioned kind can also be arranged alongside a shielded electrical signal conductor in a semiconductor structure. The plugs must be arranged so close as to obtain a good lateral shielding of the electrical signal conductor. Shielding in a vertical direction can be achieved by means of suitable metal planes below and/or above the signal conductor, which can be manufactured at the same time as other metal planes in the semiconductor structure. The plugs are preferably in electrical connection with these metal planes.